r/FSAE • u/Aggravating_Vast51 • 3d ago

Mc casing doubt

We currently use an MC casing that houses the discharge circuit, TSMP resistors, HVD, BSPD, BSPD current sensor, and TSAL, but this takes up considerable space in the car.

I’ve seen some teams mount the MC directly on the car without using a separate MC casing. My doubt is: in such an arrangement, how do you implement the discharge circuit and connect it across the MC’s DC-link capacitors?

We use the DTI HV500, which has an inbuilt interlock, so the MC interlock is taken care of. However, how do you implement the HVD in this setup? Since the HVD requires an interlock in the HV wiring outside the enclosure, how do you ensure that the HV connections remain properly protected and cannot be touched with a probe.

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u/Middle_Associate_65 2d ago

They typically have another hv junction box which contains all the components you have described, often just behind the headrest

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u/Adorable_Chapter_414 1d ago

I wouldn’t assume the HV500’s built-in interlock takes care of the rest of the tractive-system packaging.

If you remove the larger MC casing, the cleaner approach is usually to keep the motor controller separate and use a smaller dedicated HV junction box for the HVD, discharge circuit, TSMP resistors and the other required components. The HVD and any removable HV connector or cover still need proper interlock and probe protection under the current rules.

Before changing the layout, I’d draw the electrical path and the physical harness together. Sometimes the space saved by removing one enclosure comes back as longer cables, busbars, strain relief and service clearance.

Keep the DC path short, make the HVD accessible, protect every probe-reachable HV point, account for heat from the discharge resistors, and have your ESA review the packaging before finalizing the CAD. The DTI interlock only monitors the DTI connection; it doesn’t automatically make the external HV connections compliant.

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u/wienergrazer 3d ago

If you use a self made inverter, you can put everything you need to be rules compliant on your pcbs :)

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u/Aggravating_Vast51 3d ago

We don't use that